8343747: C2: TestReplicateAtConv.java crashes with -XX:MaxVectorSize=8

Reviewed-by: epeter, kvn

Author: rwestrel

src/hotspot/share/opto/vectornode.cpp

@@ -1466,6 +1466,9 @@ bool VectorCastNode::implemented(int opc, uint vlen, BasicType src_type, BasicTy
   if (is_java_primitive(dst_type) &&
       is_java_primitive(src_type) &&
       (vlen > 1) && is_power_of_2(vlen) &&
+      // In rare case, the input to the VectorCast could be a Replicate node. We need to make sure creating is supported:
+      // check the src_type:
+      VectorNode::vector_size_supported_auto_vectorization(src_type, vlen) &&
       VectorNode::vector_size_supported_auto_vectorization(dst_type, vlen)) {
     int vopc = VectorCastNode::opcode(opc, src_type);
     return vopc > 0 && Matcher::match_rule_supported_auto_vectorization(vopc, vlen, dst_type);

test/hotspot/jtreg/compiler/vectorization/TestReplicateAtConv.java

@@ -23,9 +23,10 @@
 
 /**
  * @test
- * @bug 8341834
- * @summary C2 compilation fails with "bad AD file" due to Replicate
+ * @bug 8341834 8343747
+ * @summary Replicate node at a VectorCast (ConvL2I) causes superword to fail
  * @run main/othervm -XX:CompileCommand=compileonly,TestReplicateAtConv::test -Xcomp TestReplicateAtConv
+ * @run main/othervm -XX:CompileCommand=compileonly,TestReplicateAtConv::test -Xcomp -XX:MaxVectorSize=8 TestReplicateAtConv
  */
 
 public class TestReplicateAtConv {